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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2007 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License");<a name="line.4"></a>
<span class="sourceLineNo">005</span> * you may not use this file except in compliance with the License.<a name="line.5"></a>
<span class="sourceLineNo">006</span> * You may obtain a copy of the License at<a name="line.6"></a>
<span class="sourceLineNo">007</span> *<a name="line.7"></a>
<span class="sourceLineNo">008</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * Unless required by applicable law or agreed to in writing, software<a name="line.10"></a>
<span class="sourceLineNo">011</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.11"></a>
<span class="sourceLineNo">012</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.12"></a>
<span class="sourceLineNo">013</span> * See the License for the specific language governing permissions and<a name="line.13"></a>
<span class="sourceLineNo">014</span> * limitations under the License.<a name="line.14"></a>
<span class="sourceLineNo">015</span> */<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>package com.google.common.collect;<a name="line.17"></a>
<span class="sourceLineNo">018</span><a name="line.18"></a>
<span class="sourceLineNo">019</span>import static com.google.common.base.Preconditions.checkArgument;<a name="line.19"></a>
<span class="sourceLineNo">020</span>import static com.google.common.base.Preconditions.checkNotNull;<a name="line.20"></a>
<span class="sourceLineNo">021</span>import static com.google.common.base.Preconditions.checkState;<a name="line.21"></a>
<span class="sourceLineNo">022</span>import static com.google.common.collect.Multisets.checkNonnegative;<a name="line.22"></a>
<span class="sourceLineNo">023</span><a name="line.23"></a>
<span class="sourceLineNo">024</span>import com.google.common.annotations.Beta;<a name="line.24"></a>
<span class="sourceLineNo">025</span>import com.google.common.annotations.VisibleForTesting;<a name="line.25"></a>
<span class="sourceLineNo">026</span>import com.google.common.collect.Serialization.FieldSetter;<a name="line.26"></a>
<span class="sourceLineNo">027</span>import com.google.common.math.IntMath;<a name="line.27"></a>
<span class="sourceLineNo">028</span>import com.google.common.primitives.Ints;<a name="line.28"></a>
<span class="sourceLineNo">029</span><a name="line.29"></a>
<span class="sourceLineNo">030</span>import java.io.IOException;<a name="line.30"></a>
<span class="sourceLineNo">031</span>import java.io.ObjectInputStream;<a name="line.31"></a>
<span class="sourceLineNo">032</span>import java.io.ObjectOutputStream;<a name="line.32"></a>
<span class="sourceLineNo">033</span>import java.io.Serializable;<a name="line.33"></a>
<span class="sourceLineNo">034</span>import java.util.Collection;<a name="line.34"></a>
<span class="sourceLineNo">035</span>import java.util.Iterator;<a name="line.35"></a>
<span class="sourceLineNo">036</span>import java.util.List;<a name="line.36"></a>
<span class="sourceLineNo">037</span>import java.util.Map;<a name="line.37"></a>
<span class="sourceLineNo">038</span>import java.util.Set;<a name="line.38"></a>
<span class="sourceLineNo">039</span>import java.util.concurrent.ConcurrentHashMap;<a name="line.39"></a>
<span class="sourceLineNo">040</span>import java.util.concurrent.ConcurrentMap;<a name="line.40"></a>
<span class="sourceLineNo">041</span>import java.util.concurrent.atomic.AtomicInteger;<a name="line.41"></a>
<span class="sourceLineNo">042</span><a name="line.42"></a>
<span class="sourceLineNo">043</span>import javax.annotation.Nullable;<a name="line.43"></a>
<span class="sourceLineNo">044</span><a name="line.44"></a>
<span class="sourceLineNo">045</span>/**<a name="line.45"></a>
<span class="sourceLineNo">046</span> * A multiset that supports concurrent modifications and that provides atomic versions of most<a name="line.46"></a>
<span class="sourceLineNo">047</span> * {@code Multiset} operations (exceptions where noted). Null elements are not supported.<a name="line.47"></a>
<span class="sourceLineNo">048</span> *<a name="line.48"></a>
<span class="sourceLineNo">049</span> * &lt;p&gt;See the Guava User Guide article on &lt;a href=<a name="line.49"></a>
<span class="sourceLineNo">050</span> * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#Multiset"&gt;<a name="line.50"></a>
<span class="sourceLineNo">051</span> * {@code Multiset}&lt;/a&gt;.<a name="line.51"></a>
<span class="sourceLineNo">052</span> *<a name="line.52"></a>
<span class="sourceLineNo">053</span> * @author Cliff L. Biffle<a name="line.53"></a>
<span class="sourceLineNo">054</span> * @author mike nonemacher<a name="line.54"></a>
<span class="sourceLineNo">055</span> * @since 2.0 (imported from Google Collections Library)<a name="line.55"></a>
<span class="sourceLineNo">056</span> */<a name="line.56"></a>
<span class="sourceLineNo">057</span>public final class ConcurrentHashMultiset&lt;E&gt; extends AbstractMultiset&lt;E&gt; implements Serializable {<a name="line.57"></a>
<span class="sourceLineNo">058</span><a name="line.58"></a>
<span class="sourceLineNo">059</span>  /*<a name="line.59"></a>
<span class="sourceLineNo">060</span>   * The ConcurrentHashMultiset's atomic operations are implemented primarily in terms of<a name="line.60"></a>
<span class="sourceLineNo">061</span>   * AtomicInteger's atomic operations, with some help from ConcurrentMap's atomic operations on<a name="line.61"></a>
<span class="sourceLineNo">062</span>   * creation and removal (including automatic removal of zeroes). If the modification of an<a name="line.62"></a>
<span class="sourceLineNo">063</span>   * AtomicInteger results in zero, we compareAndSet the value to zero; if that succeeds, we remove<a name="line.63"></a>
<span class="sourceLineNo">064</span>   * the entry from the Map. If another operation sees a zero in the map, it knows that the entry is<a name="line.64"></a>
<span class="sourceLineNo">065</span>   * about to be removed, so this operation may remove it (often by replacing it with a new<a name="line.65"></a>
<span class="sourceLineNo">066</span>   * AtomicInteger).<a name="line.66"></a>
<span class="sourceLineNo">067</span>   */<a name="line.67"></a>
<span class="sourceLineNo">068</span><a name="line.68"></a>
<span class="sourceLineNo">069</span>  /** The number of occurrences of each element. */<a name="line.69"></a>
<span class="sourceLineNo">070</span>  private final transient ConcurrentMap&lt;E, AtomicInteger&gt; countMap;<a name="line.70"></a>
<span class="sourceLineNo">071</span><a name="line.71"></a>
<span class="sourceLineNo">072</span>  // This constant allows the deserialization code to set a final field. This holder class<a name="line.72"></a>
<span class="sourceLineNo">073</span>  // makes sure it is not initialized unless an instance is deserialized.<a name="line.73"></a>
<span class="sourceLineNo">074</span>  private static class FieldSettersHolder {<a name="line.74"></a>
<span class="sourceLineNo">075</span>    static final FieldSetter&lt;ConcurrentHashMultiset&gt; COUNT_MAP_FIELD_SETTER =<a name="line.75"></a>
<span class="sourceLineNo">076</span>        Serialization.getFieldSetter(ConcurrentHashMultiset.class, "countMap");<a name="line.76"></a>
<span class="sourceLineNo">077</span>  }<a name="line.77"></a>
<span class="sourceLineNo">078</span><a name="line.78"></a>
<span class="sourceLineNo">079</span>  /**<a name="line.79"></a>
<span class="sourceLineNo">080</span>   * Creates a new, empty {@code ConcurrentHashMultiset} using the default<a name="line.80"></a>
<span class="sourceLineNo">081</span>   * initial capacity, load factor, and concurrency settings.<a name="line.81"></a>
<span class="sourceLineNo">082</span>   */<a name="line.82"></a>
<span class="sourceLineNo">083</span>  public static &lt;E&gt; ConcurrentHashMultiset&lt;E&gt; create() {<a name="line.83"></a>
<span class="sourceLineNo">084</span>    // TODO(schmoe): provide a way to use this class with other (possibly arbitrary)<a name="line.84"></a>
<span class="sourceLineNo">085</span>    // ConcurrentMap implementors. One possibility is to extract most of this class into<a name="line.85"></a>
<span class="sourceLineNo">086</span>    // an AbstractConcurrentMapMultiset.<a name="line.86"></a>
<span class="sourceLineNo">087</span>    return new ConcurrentHashMultiset&lt;E&gt;(new ConcurrentHashMap&lt;E, AtomicInteger&gt;());<a name="line.87"></a>
<span class="sourceLineNo">088</span>  }<a name="line.88"></a>
<span class="sourceLineNo">089</span><a name="line.89"></a>
<span class="sourceLineNo">090</span>  /**<a name="line.90"></a>
<span class="sourceLineNo">091</span>   * Creates a new {@code ConcurrentHashMultiset} containing the specified elements, using<a name="line.91"></a>
<span class="sourceLineNo">092</span>   * the default initial capacity, load factor, and concurrency settings.<a name="line.92"></a>
<span class="sourceLineNo">093</span>   *<a name="line.93"></a>
<span class="sourceLineNo">094</span>   * &lt;p&gt;This implementation is highly efficient when {@code elements} is itself a {@link Multiset}.<a name="line.94"></a>
<span class="sourceLineNo">095</span>   *<a name="line.95"></a>
<span class="sourceLineNo">096</span>   * @param elements the elements that the multiset should contain<a name="line.96"></a>
<span class="sourceLineNo">097</span>   */<a name="line.97"></a>
<span class="sourceLineNo">098</span>  public static &lt;E&gt; ConcurrentHashMultiset&lt;E&gt; create(Iterable&lt;? extends E&gt; elements) {<a name="line.98"></a>
<span class="sourceLineNo">099</span>    ConcurrentHashMultiset&lt;E&gt; multiset = ConcurrentHashMultiset.create();<a name="line.99"></a>
<span class="sourceLineNo">100</span>    Iterables.addAll(multiset, elements);<a name="line.100"></a>
<span class="sourceLineNo">101</span>    return multiset;<a name="line.101"></a>
<span class="sourceLineNo">102</span>  }<a name="line.102"></a>
<span class="sourceLineNo">103</span><a name="line.103"></a>
<span class="sourceLineNo">104</span>  /**<a name="line.104"></a>
<span class="sourceLineNo">105</span>   * Creates a new, empty {@code ConcurrentHashMultiset} using {@code mapMaker}<a name="line.105"></a>
<span class="sourceLineNo">106</span>   * to construct the internal backing map.<a name="line.106"></a>
<span class="sourceLineNo">107</span>   *<a name="line.107"></a>
<span class="sourceLineNo">108</span>   * &lt;p&gt;If this {@link MapMaker} is configured to use entry eviction of any kind, this eviction<a name="line.108"></a>
<span class="sourceLineNo">109</span>   * applies to all occurrences of a given element as a single unit. However, most updates to the<a name="line.109"></a>
<span class="sourceLineNo">110</span>   * multiset do not count as map updates at all, since we're usually just mutating the value<a name="line.110"></a>
<span class="sourceLineNo">111</span>   * stored in the map, so {@link MapMaker#expireAfterAccess} makes sense (evict the entry that<a name="line.111"></a>
<span class="sourceLineNo">112</span>   * was queried or updated longest ago), but {@link MapMaker#expireAfterWrite} doesn't, because<a name="line.112"></a>
<span class="sourceLineNo">113</span>   * the eviction time is measured from when we saw the first occurrence of the object.<a name="line.113"></a>
<span class="sourceLineNo">114</span>   *<a name="line.114"></a>
<span class="sourceLineNo">115</span>   * &lt;p&gt;The returned multiset is serializable but any serialization caveats<a name="line.115"></a>
<span class="sourceLineNo">116</span>   * given in {@code MapMaker} apply.<a name="line.116"></a>
<span class="sourceLineNo">117</span>   *<a name="line.117"></a>
<span class="sourceLineNo">118</span>   * &lt;p&gt;Finally, soft/weak values can be used but are not very useful: the values are created<a name="line.118"></a>
<span class="sourceLineNo">119</span>   * internally and not exposed externally, so no one else will have a strong reference to the<a name="line.119"></a>
<span class="sourceLineNo">120</span>   * values. Weak keys on the other hand can be useful in some scenarios.<a name="line.120"></a>
<span class="sourceLineNo">121</span>   *<a name="line.121"></a>
<span class="sourceLineNo">122</span>   * @since 7.0<a name="line.122"></a>
<span class="sourceLineNo">123</span>   */<a name="line.123"></a>
<span class="sourceLineNo">124</span>  @Beta<a name="line.124"></a>
<span class="sourceLineNo">125</span>  public static &lt;E&gt; ConcurrentHashMultiset&lt;E&gt; create(<a name="line.125"></a>
<span class="sourceLineNo">126</span>      GenericMapMaker&lt;? super E, ? super Number&gt; mapMaker) {<a name="line.126"></a>
<span class="sourceLineNo">127</span>    return new ConcurrentHashMultiset&lt;E&gt;(mapMaker.&lt;E, AtomicInteger&gt;makeMap());<a name="line.127"></a>
<span class="sourceLineNo">128</span>  }<a name="line.128"></a>
<span class="sourceLineNo">129</span><a name="line.129"></a>
<span class="sourceLineNo">130</span>  /**<a name="line.130"></a>
<span class="sourceLineNo">131</span>   * Creates an instance using {@code countMap} to store elements and their counts.<a name="line.131"></a>
<span class="sourceLineNo">132</span>   *<a name="line.132"></a>
<span class="sourceLineNo">133</span>   * &lt;p&gt;This instance will assume ownership of {@code countMap}, and other code<a name="line.133"></a>
<span class="sourceLineNo">134</span>   * should not maintain references to the map or modify it in any way.<a name="line.134"></a>
<span class="sourceLineNo">135</span>   *<a name="line.135"></a>
<span class="sourceLineNo">136</span>   * @param countMap backing map for storing the elements in the multiset and<a name="line.136"></a>
<span class="sourceLineNo">137</span>   *     their counts. It must be empty.<a name="line.137"></a>
<span class="sourceLineNo">138</span>   * @throws IllegalArgumentException if {@code countMap} is not empty<a name="line.138"></a>
<span class="sourceLineNo">139</span>   */<a name="line.139"></a>
<span class="sourceLineNo">140</span>  @VisibleForTesting ConcurrentHashMultiset(ConcurrentMap&lt;E, AtomicInteger&gt; countMap) {<a name="line.140"></a>
<span class="sourceLineNo">141</span>    checkArgument(countMap.isEmpty());<a name="line.141"></a>
<span class="sourceLineNo">142</span>    this.countMap = countMap;<a name="line.142"></a>
<span class="sourceLineNo">143</span>  }<a name="line.143"></a>
<span class="sourceLineNo">144</span><a name="line.144"></a>
<span class="sourceLineNo">145</span>  // Query Operations<a name="line.145"></a>
<span class="sourceLineNo">146</span><a name="line.146"></a>
<span class="sourceLineNo">147</span>  /**<a name="line.147"></a>
<span class="sourceLineNo">148</span>   * Returns the number of occurrences of {@code element} in this multiset.<a name="line.148"></a>
<span class="sourceLineNo">149</span>   *<a name="line.149"></a>
<span class="sourceLineNo">150</span>   * @param element the element to look for<a name="line.150"></a>
<span class="sourceLineNo">151</span>   * @return the nonnegative number of occurrences of the element<a name="line.151"></a>
<span class="sourceLineNo">152</span>   */<a name="line.152"></a>
<span class="sourceLineNo">153</span>  @Override public int count(@Nullable Object element) {<a name="line.153"></a>
<span class="sourceLineNo">154</span>    AtomicInteger existingCounter = safeGet(element);<a name="line.154"></a>
<span class="sourceLineNo">155</span>    return (existingCounter == null) ? 0 : existingCounter.get();<a name="line.155"></a>
<span class="sourceLineNo">156</span>  }<a name="line.156"></a>
<span class="sourceLineNo">157</span><a name="line.157"></a>
<span class="sourceLineNo">158</span>  /**<a name="line.158"></a>
<span class="sourceLineNo">159</span>   * Depending on the type of the underlying map, map.get may throw NullPointerException or<a name="line.159"></a>
<span class="sourceLineNo">160</span>   * ClassCastException, if the object is null or of the wrong type. We usually just want to treat<a name="line.160"></a>
<span class="sourceLineNo">161</span>   * those cases as if the element isn't in the map, by catching the exceptions and returning null.<a name="line.161"></a>
<span class="sourceLineNo">162</span>   */<a name="line.162"></a>
<span class="sourceLineNo">163</span>  private AtomicInteger safeGet(Object element) {<a name="line.163"></a>
<span class="sourceLineNo">164</span>    try {<a name="line.164"></a>
<span class="sourceLineNo">165</span>      return countMap.get(element);<a name="line.165"></a>
<span class="sourceLineNo">166</span>    } catch (NullPointerException e) {<a name="line.166"></a>
<span class="sourceLineNo">167</span>      return null;<a name="line.167"></a>
<span class="sourceLineNo">168</span>    } catch (ClassCastException e) {<a name="line.168"></a>
<span class="sourceLineNo">169</span>      return null;<a name="line.169"></a>
<span class="sourceLineNo">170</span>    }<a name="line.170"></a>
<span class="sourceLineNo">171</span>  }<a name="line.171"></a>
<span class="sourceLineNo">172</span><a name="line.172"></a>
<span class="sourceLineNo">173</span>  /**<a name="line.173"></a>
<span class="sourceLineNo">174</span>   * {@inheritDoc}<a name="line.174"></a>
<span class="sourceLineNo">175</span>   *<a name="line.175"></a>
<span class="sourceLineNo">176</span>   * &lt;p&gt;If the data in the multiset is modified by any other threads during this method,<a name="line.176"></a>
<span class="sourceLineNo">177</span>   * it is undefined which (if any) of these modifications will be reflected in the result.<a name="line.177"></a>
<span class="sourceLineNo">178</span>   */<a name="line.178"></a>
<span class="sourceLineNo">179</span>  @Override public int size() {<a name="line.179"></a>
<span class="sourceLineNo">180</span>    long sum = 0L;<a name="line.180"></a>
<span class="sourceLineNo">181</span>    for (AtomicInteger value : countMap.values()) {<a name="line.181"></a>
<span class="sourceLineNo">182</span>      sum += value.get();<a name="line.182"></a>
<span class="sourceLineNo">183</span>    }<a name="line.183"></a>
<span class="sourceLineNo">184</span>    return Ints.saturatedCast(sum);<a name="line.184"></a>
<span class="sourceLineNo">185</span>  }<a name="line.185"></a>
<span class="sourceLineNo">186</span><a name="line.186"></a>
<span class="sourceLineNo">187</span>  /*<a name="line.187"></a>
<span class="sourceLineNo">188</span>   * Note: the superclass toArray() methods assume that size() gives a correct<a name="line.188"></a>
<span class="sourceLineNo">189</span>   * answer, which ours does not.<a name="line.189"></a>
<span class="sourceLineNo">190</span>   */<a name="line.190"></a>
<span class="sourceLineNo">191</span><a name="line.191"></a>
<span class="sourceLineNo">192</span>  @Override public Object[] toArray() {<a name="line.192"></a>
<span class="sourceLineNo">193</span>    return snapshot().toArray();<a name="line.193"></a>
<span class="sourceLineNo">194</span>  }<a name="line.194"></a>
<span class="sourceLineNo">195</span><a name="line.195"></a>
<span class="sourceLineNo">196</span>  @Override public &lt;T&gt; T[] toArray(T[] array) {<a name="line.196"></a>
<span class="sourceLineNo">197</span>    return snapshot().toArray(array);<a name="line.197"></a>
<span class="sourceLineNo">198</span>  }<a name="line.198"></a>
<span class="sourceLineNo">199</span><a name="line.199"></a>
<span class="sourceLineNo">200</span>  /*<a name="line.200"></a>
<span class="sourceLineNo">201</span>   * We'd love to use 'new ArrayList(this)' or 'list.addAll(this)', but<a name="line.201"></a>
<span class="sourceLineNo">202</span>   * either of these would recurse back to us again!<a name="line.202"></a>
<span class="sourceLineNo">203</span>   */<a name="line.203"></a>
<span class="sourceLineNo">204</span>  private List&lt;E&gt; snapshot() {<a name="line.204"></a>
<span class="sourceLineNo">205</span>    List&lt;E&gt; list = Lists.newArrayListWithExpectedSize(size());<a name="line.205"></a>
<span class="sourceLineNo">206</span>    for (Multiset.Entry&lt;E&gt; entry : entrySet()) {<a name="line.206"></a>
<span class="sourceLineNo">207</span>      E element = entry.getElement();<a name="line.207"></a>
<span class="sourceLineNo">208</span>      for (int i = entry.getCount(); i &gt; 0; i--) {<a name="line.208"></a>
<span class="sourceLineNo">209</span>        list.add(element);<a name="line.209"></a>
<span class="sourceLineNo">210</span>      }<a name="line.210"></a>
<span class="sourceLineNo">211</span>    }<a name="line.211"></a>
<span class="sourceLineNo">212</span>    return list;<a name="line.212"></a>
<span class="sourceLineNo">213</span>  }<a name="line.213"></a>
<span class="sourceLineNo">214</span><a name="line.214"></a>
<span class="sourceLineNo">215</span>  // Modification Operations<a name="line.215"></a>
<span class="sourceLineNo">216</span><a name="line.216"></a>
<span class="sourceLineNo">217</span>  /**<a name="line.217"></a>
<span class="sourceLineNo">218</span>   * Adds a number of occurrences of the specified element to this multiset.<a name="line.218"></a>
<span class="sourceLineNo">219</span>   *<a name="line.219"></a>
<span class="sourceLineNo">220</span>   * @param element the element to add<a name="line.220"></a>
<span class="sourceLineNo">221</span>   * @param occurrences the number of occurrences to add<a name="line.221"></a>
<span class="sourceLineNo">222</span>   * @return the previous count of the element before the operation; possibly zero<a name="line.222"></a>
<span class="sourceLineNo">223</span>   * @throws IllegalArgumentException if {@code occurrences} is negative, or if<a name="line.223"></a>
<span class="sourceLineNo">224</span>   *     the resulting amount would exceed {@link Integer#MAX_VALUE}<a name="line.224"></a>
<span class="sourceLineNo">225</span>   */<a name="line.225"></a>
<span class="sourceLineNo">226</span>  @Override public int add(E element, int occurrences) {<a name="line.226"></a>
<span class="sourceLineNo">227</span>    checkNotNull(element);<a name="line.227"></a>
<span class="sourceLineNo">228</span>    if (occurrences == 0) {<a name="line.228"></a>
<span class="sourceLineNo">229</span>      return count(element);<a name="line.229"></a>
<span class="sourceLineNo">230</span>    }<a name="line.230"></a>
<span class="sourceLineNo">231</span>    checkArgument(occurrences &gt; 0, "Invalid occurrences: %s", occurrences);<a name="line.231"></a>
<span class="sourceLineNo">232</span><a name="line.232"></a>
<span class="sourceLineNo">233</span>    while (true) {<a name="line.233"></a>
<span class="sourceLineNo">234</span>      AtomicInteger existingCounter = safeGet(element);<a name="line.234"></a>
<span class="sourceLineNo">235</span>      if (existingCounter == null) {<a name="line.235"></a>
<span class="sourceLineNo">236</span>        existingCounter = countMap.putIfAbsent(element, new AtomicInteger(occurrences));<a name="line.236"></a>
<span class="sourceLineNo">237</span>        if (existingCounter == null) {<a name="line.237"></a>
<span class="sourceLineNo">238</span>          return 0;<a name="line.238"></a>
<span class="sourceLineNo">239</span>        }<a name="line.239"></a>
<span class="sourceLineNo">240</span>        // existingCounter != null: fall through to operate against the existing AtomicInteger<a name="line.240"></a>
<span class="sourceLineNo">241</span>      }<a name="line.241"></a>
<span class="sourceLineNo">242</span><a name="line.242"></a>
<span class="sourceLineNo">243</span>      while (true) {<a name="line.243"></a>
<span class="sourceLineNo">244</span>        int oldValue = existingCounter.get();<a name="line.244"></a>
<span class="sourceLineNo">245</span>        if (oldValue != 0) {<a name="line.245"></a>
<span class="sourceLineNo">246</span>          try {<a name="line.246"></a>
<span class="sourceLineNo">247</span>            int newValue = IntMath.checkedAdd(oldValue, occurrences);<a name="line.247"></a>
<span class="sourceLineNo">248</span>            if (existingCounter.compareAndSet(oldValue, newValue)) {<a name="line.248"></a>
<span class="sourceLineNo">249</span>              // newValue can't == 0, so no need to check &amp; remove<a name="line.249"></a>
<span class="sourceLineNo">250</span>              return oldValue;<a name="line.250"></a>
<span class="sourceLineNo">251</span>            }<a name="line.251"></a>
<span class="sourceLineNo">252</span>          } catch (ArithmeticException overflow) {<a name="line.252"></a>
<span class="sourceLineNo">253</span>            throw new IllegalArgumentException("Overflow adding " + occurrences<a name="line.253"></a>
<span class="sourceLineNo">254</span>                + " occurrences to a count of " + oldValue);<a name="line.254"></a>
<span class="sourceLineNo">255</span>          }<a name="line.255"></a>
<span class="sourceLineNo">256</span>        } else {<a name="line.256"></a>
<span class="sourceLineNo">257</span>          // In the case of a concurrent remove, we might observe a zero value, which means another<a name="line.257"></a>
<span class="sourceLineNo">258</span>          // thread is about to remove (element, existingCounter) from the map. Rather than wait,<a name="line.258"></a>
<span class="sourceLineNo">259</span>          // we can just do that work here.<a name="line.259"></a>
<span class="sourceLineNo">260</span>          AtomicInteger newCounter = new AtomicInteger(occurrences);<a name="line.260"></a>
<span class="sourceLineNo">261</span>          if ((countMap.putIfAbsent(element, newCounter) == null)<a name="line.261"></a>
<span class="sourceLineNo">262</span>              || countMap.replace(element, existingCounter, newCounter)) {<a name="line.262"></a>
<span class="sourceLineNo">263</span>            return 0;<a name="line.263"></a>
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<span class="sourceLineNo">268</span><a name="line.268"></a>
<span class="sourceLineNo">269</span>      // If we're still here, there was a race, so just try again.<a name="line.269"></a>
<span class="sourceLineNo">270</span>    }<a name="line.270"></a>
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<span class="sourceLineNo">272</span><a name="line.272"></a>
<span class="sourceLineNo">273</span>  /**<a name="line.273"></a>
<span class="sourceLineNo">274</span>   * Removes a number of occurrences of the specified element from this multiset. If the multiset<a name="line.274"></a>
<span class="sourceLineNo">275</span>   * contains fewer than this number of occurrences to begin with, all occurrences will be removed.<a name="line.275"></a>
<span class="sourceLineNo">276</span>   *<a name="line.276"></a>
<span class="sourceLineNo">277</span>   * @param element the element whose occurrences should be removed<a name="line.277"></a>
<span class="sourceLineNo">278</span>   * @param occurrences the number of occurrences of the element to remove<a name="line.278"></a>
<span class="sourceLineNo">279</span>   * @return the count of the element before the operation; possibly zero<a name="line.279"></a>
<span class="sourceLineNo">280</span>   * @throws IllegalArgumentException if {@code occurrences} is negative<a name="line.280"></a>
<span class="sourceLineNo">281</span>   */<a name="line.281"></a>
<span class="sourceLineNo">282</span>  /*<a name="line.282"></a>
<span class="sourceLineNo">283</span>   * TODO(cpovirk): remove and removeExactly currently accept null inputs only<a name="line.283"></a>
<span class="sourceLineNo">284</span>   * if occurrences == 0. This satisfies both NullPointerTester and<a name="line.284"></a>
<span class="sourceLineNo">285</span>   * CollectionRemoveTester.testRemove_nullAllowed, but it's not clear that it's<a name="line.285"></a>
<span class="sourceLineNo">286</span>   * a good policy, especially because, in order for the test to pass, the<a name="line.286"></a>
<span class="sourceLineNo">287</span>   * parameter must be misleadingly annotated as @Nullable. I suspect that<a name="line.287"></a>
<span class="sourceLineNo">288</span>   * we'll want to remove @Nullable, add an eager checkNotNull, and loosen up<a name="line.288"></a>
<span class="sourceLineNo">289</span>   * testRemove_nullAllowed.<a name="line.289"></a>
<span class="sourceLineNo">290</span>   */<a name="line.290"></a>
<span class="sourceLineNo">291</span>  @Override public int remove(@Nullable Object element, int occurrences) {<a name="line.291"></a>
<span class="sourceLineNo">292</span>    if (occurrences == 0) {<a name="line.292"></a>
<span class="sourceLineNo">293</span>      return count(element);<a name="line.293"></a>
<span class="sourceLineNo">294</span>    }<a name="line.294"></a>
<span class="sourceLineNo">295</span>    checkArgument(occurrences &gt; 0, "Invalid occurrences: %s", occurrences);<a name="line.295"></a>
<span class="sourceLineNo">296</span><a name="line.296"></a>
<span class="sourceLineNo">297</span>    AtomicInteger existingCounter = safeGet(element);<a name="line.297"></a>
<span class="sourceLineNo">298</span>    if (existingCounter == null) {<a name="line.298"></a>
<span class="sourceLineNo">299</span>      return 0;<a name="line.299"></a>
<span class="sourceLineNo">300</span>    }<a name="line.300"></a>
<span class="sourceLineNo">301</span>    while (true) {<a name="line.301"></a>
<span class="sourceLineNo">302</span>      int oldValue = existingCounter.get();<a name="line.302"></a>
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<span class="sourceLineNo">304</span>        int newValue = Math.max(0, oldValue - occurrences);<a name="line.304"></a>
<span class="sourceLineNo">305</span>        if (existingCounter.compareAndSet(oldValue, newValue)) {<a name="line.305"></a>
<span class="sourceLineNo">306</span>          if (newValue == 0) {<a name="line.306"></a>
<span class="sourceLineNo">307</span>            // Just CASed to 0; remove the entry to clean up the map. If the removal fails,<a name="line.307"></a>
<span class="sourceLineNo">308</span>            // another thread has already replaced it with a new counter, which is fine.<a name="line.308"></a>
<span class="sourceLineNo">309</span>            countMap.remove(element, existingCounter);<a name="line.309"></a>
<span class="sourceLineNo">310</span>          }<a name="line.310"></a>
<span class="sourceLineNo">311</span>          return oldValue;<a name="line.311"></a>
<span class="sourceLineNo">312</span>        }<a name="line.312"></a>
<span class="sourceLineNo">313</span>      } else {<a name="line.313"></a>
<span class="sourceLineNo">314</span>        return 0;<a name="line.314"></a>
<span class="sourceLineNo">315</span>      }<a name="line.315"></a>
<span class="sourceLineNo">316</span>    }<a name="line.316"></a>
<span class="sourceLineNo">317</span>  }<a name="line.317"></a>
<span class="sourceLineNo">318</span><a name="line.318"></a>
<span class="sourceLineNo">319</span>  /**<a name="line.319"></a>
<span class="sourceLineNo">320</span>   * Removes exactly the specified number of occurrences of {@code element}, or makes no<a name="line.320"></a>
<span class="sourceLineNo">321</span>   * change if this is not possible.<a name="line.321"></a>
<span class="sourceLineNo">322</span>   *<a name="line.322"></a>
<span class="sourceLineNo">323</span>   * &lt;p&gt;This method, in contrast to {@link #remove(Object, int)}, has no effect when the<a name="line.323"></a>
<span class="sourceLineNo">324</span>   * element count is smaller than {@code occurrences}.<a name="line.324"></a>
<span class="sourceLineNo">325</span>   *<a name="line.325"></a>
<span class="sourceLineNo">326</span>   * @param element the element to remove<a name="line.326"></a>
<span class="sourceLineNo">327</span>   * @param occurrences the number of occurrences of {@code element} to remove<a name="line.327"></a>
<span class="sourceLineNo">328</span>   * @return {@code true} if the removal was possible (including if {@code occurrences} is zero)<a name="line.328"></a>
<span class="sourceLineNo">329</span>   */<a name="line.329"></a>
<span class="sourceLineNo">330</span>  public boolean removeExactly(@Nullable Object element, int occurrences) {<a name="line.330"></a>
<span class="sourceLineNo">331</span>    if (occurrences == 0) {<a name="line.331"></a>
<span class="sourceLineNo">332</span>      return true;<a name="line.332"></a>
<span class="sourceLineNo">333</span>    }<a name="line.333"></a>
<span class="sourceLineNo">334</span>    checkArgument(occurrences &gt; 0, "Invalid occurrences: %s", occurrences);<a name="line.334"></a>
<span class="sourceLineNo">335</span><a name="line.335"></a>
<span class="sourceLineNo">336</span>    AtomicInteger existingCounter = safeGet(element);<a name="line.336"></a>
<span class="sourceLineNo">337</span>    if (existingCounter == null) {<a name="line.337"></a>
<span class="sourceLineNo">338</span>      return false;<a name="line.338"></a>
<span class="sourceLineNo">339</span>    }<a name="line.339"></a>
<span class="sourceLineNo">340</span>    while (true) {<a name="line.340"></a>
<span class="sourceLineNo">341</span>      int oldValue = existingCounter.get();<a name="line.341"></a>
<span class="sourceLineNo">342</span>      if (oldValue &lt; occurrences) {<a name="line.342"></a>
<span class="sourceLineNo">343</span>        return false;<a name="line.343"></a>
<span class="sourceLineNo">344</span>      }<a name="line.344"></a>
<span class="sourceLineNo">345</span>      int newValue = oldValue - occurrences;<a name="line.345"></a>
<span class="sourceLineNo">346</span>      if (existingCounter.compareAndSet(oldValue, newValue)) {<a name="line.346"></a>
<span class="sourceLineNo">347</span>        if (newValue == 0) {<a name="line.347"></a>
<span class="sourceLineNo">348</span>          // Just CASed to 0; remove the entry to clean up the map. If the removal fails,<a name="line.348"></a>
<span class="sourceLineNo">349</span>          // another thread has already replaced it with a new counter, which is fine.<a name="line.349"></a>
<span class="sourceLineNo">350</span>          countMap.remove(element, existingCounter);<a name="line.350"></a>
<span class="sourceLineNo">351</span>        }<a name="line.351"></a>
<span class="sourceLineNo">352</span>        return true;<a name="line.352"></a>
<span class="sourceLineNo">353</span>      }<a name="line.353"></a>
<span class="sourceLineNo">354</span>    }<a name="line.354"></a>
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<span class="sourceLineNo">358</span>   * Adds or removes occurrences of {@code element} such that the {@link #count} of the<a name="line.358"></a>
<span class="sourceLineNo">359</span>   * element becomes {@code count}.<a name="line.359"></a>
<span class="sourceLineNo">360</span>   *<a name="line.360"></a>
<span class="sourceLineNo">361</span>   * @return the count of {@code element} in the multiset before this call<a name="line.361"></a>
<span class="sourceLineNo">362</span>   * @throws IllegalArgumentException if {@code count} is negative<a name="line.362"></a>
<span class="sourceLineNo">363</span>   */<a name="line.363"></a>
<span class="sourceLineNo">364</span>  @Override public int setCount(E element, int count) {<a name="line.364"></a>
<span class="sourceLineNo">365</span>    checkNotNull(element);<a name="line.365"></a>
<span class="sourceLineNo">366</span>    checkNonnegative(count, "count");<a name="line.366"></a>
<span class="sourceLineNo">367</span>    while (true) {<a name="line.367"></a>
<span class="sourceLineNo">368</span>      AtomicInteger existingCounter = safeGet(element);<a name="line.368"></a>
<span class="sourceLineNo">369</span>      if (existingCounter == null) {<a name="line.369"></a>
<span class="sourceLineNo">370</span>        if (count == 0) {<a name="line.370"></a>
<span class="sourceLineNo">371</span>          return 0;<a name="line.371"></a>
<span class="sourceLineNo">372</span>        } else {<a name="line.372"></a>
<span class="sourceLineNo">373</span>          existingCounter = countMap.putIfAbsent(element, new AtomicInteger(count));<a name="line.373"></a>
<span class="sourceLineNo">374</span>          if (existingCounter == null) {<a name="line.374"></a>
<span class="sourceLineNo">375</span>            return 0;<a name="line.375"></a>
<span class="sourceLineNo">376</span>          }<a name="line.376"></a>
<span class="sourceLineNo">377</span>          // existingCounter != null: fall through<a name="line.377"></a>
<span class="sourceLineNo">378</span>        }<a name="line.378"></a>
<span class="sourceLineNo">379</span>      }<a name="line.379"></a>
<span class="sourceLineNo">380</span><a name="line.380"></a>
<span class="sourceLineNo">381</span>      while (true) {<a name="line.381"></a>
<span class="sourceLineNo">382</span>        int oldValue = existingCounter.get();<a name="line.382"></a>
<span class="sourceLineNo">383</span>        if (oldValue == 0) {<a name="line.383"></a>
<span class="sourceLineNo">384</span>          if (count == 0) {<a name="line.384"></a>
<span class="sourceLineNo">385</span>            return 0;<a name="line.385"></a>
<span class="sourceLineNo">386</span>          } else {<a name="line.386"></a>
<span class="sourceLineNo">387</span>            AtomicInteger newCounter = new AtomicInteger(count);<a name="line.387"></a>
<span class="sourceLineNo">388</span>            if ((countMap.putIfAbsent(element, newCounter) == null)<a name="line.388"></a>
<span class="sourceLineNo">389</span>                || countMap.replace(element, existingCounter, newCounter)) {<a name="line.389"></a>
<span class="sourceLineNo">390</span>              return 0;<a name="line.390"></a>
<span class="sourceLineNo">391</span>            }<a name="line.391"></a>
<span class="sourceLineNo">392</span>          }<a name="line.392"></a>
<span class="sourceLineNo">393</span>          break;<a name="line.393"></a>
<span class="sourceLineNo">394</span>        } else {<a name="line.394"></a>
<span class="sourceLineNo">395</span>          if (existingCounter.compareAndSet(oldValue, count)) {<a name="line.395"></a>
<span class="sourceLineNo">396</span>            if (count == 0) {<a name="line.396"></a>
<span class="sourceLineNo">397</span>              // Just CASed to 0; remove the entry to clean up the map. If the removal fails,<a name="line.397"></a>
<span class="sourceLineNo">398</span>              // another thread has already replaced it with a new counter, which is fine.<a name="line.398"></a>
<span class="sourceLineNo">399</span>              countMap.remove(element, existingCounter);<a name="line.399"></a>
<span class="sourceLineNo">400</span>            }<a name="line.400"></a>
<span class="sourceLineNo">401</span>            return oldValue;<a name="line.401"></a>
<span class="sourceLineNo">402</span>          }<a name="line.402"></a>
<span class="sourceLineNo">403</span>        }<a name="line.403"></a>
<span class="sourceLineNo">404</span>      }<a name="line.404"></a>
<span class="sourceLineNo">405</span>    }<a name="line.405"></a>
<span class="sourceLineNo">406</span>  }<a name="line.406"></a>
<span class="sourceLineNo">407</span><a name="line.407"></a>
<span class="sourceLineNo">408</span>  /**<a name="line.408"></a>
<span class="sourceLineNo">409</span>   * Sets the number of occurrences of {@code element} to {@code newCount}, but only if<a name="line.409"></a>
<span class="sourceLineNo">410</span>   * the count is currently {@code expectedOldCount}. If {@code element} does not appear<a name="line.410"></a>
<span class="sourceLineNo">411</span>   * in the multiset exactly {@code expectedOldCount} times, no changes will be made.<a name="line.411"></a>
<span class="sourceLineNo">412</span>   *<a name="line.412"></a>
<span class="sourceLineNo">413</span>   * @return {@code true} if the change was successful. This usually indicates<a name="line.413"></a>
<span class="sourceLineNo">414</span>   *     that the multiset has been modified, but not always: in the case that<a name="line.414"></a>
<span class="sourceLineNo">415</span>   *     {@code expectedOldCount == newCount}, the method will return {@code true} if<a name="line.415"></a>
<span class="sourceLineNo">416</span>   *     the condition was met.<a name="line.416"></a>
<span class="sourceLineNo">417</span>   * @throws IllegalArgumentException if {@code expectedOldCount} or {@code newCount} is negative<a name="line.417"></a>
<span class="sourceLineNo">418</span>   */<a name="line.418"></a>
<span class="sourceLineNo">419</span>  @Override public boolean setCount(E element, int expectedOldCount, int newCount) {<a name="line.419"></a>
<span class="sourceLineNo">420</span>    checkNotNull(element);<a name="line.420"></a>
<span class="sourceLineNo">421</span>    checkNonnegative(expectedOldCount, "oldCount");<a name="line.421"></a>
<span class="sourceLineNo">422</span>    checkNonnegative(newCount, "newCount");<a name="line.422"></a>
<span class="sourceLineNo">423</span><a name="line.423"></a>
<span class="sourceLineNo">424</span>    AtomicInteger existingCounter = safeGet(element);<a name="line.424"></a>
<span class="sourceLineNo">425</span>    if (existingCounter == null) {<a name="line.425"></a>
<span class="sourceLineNo">426</span>      if (expectedOldCount != 0) {<a name="line.426"></a>
<span class="sourceLineNo">427</span>        return false;<a name="line.427"></a>
<span class="sourceLineNo">428</span>      } else if (newCount == 0) {<a name="line.428"></a>
<span class="sourceLineNo">429</span>        return true;<a name="line.429"></a>
<span class="sourceLineNo">430</span>      } else {<a name="line.430"></a>
<span class="sourceLineNo">431</span>        // if our write lost the race, it must have lost to a nonzero value, so we can stop<a name="line.431"></a>
<span class="sourceLineNo">432</span>        return countMap.putIfAbsent(element, new AtomicInteger(newCount)) == null;<a name="line.432"></a>
<span class="sourceLineNo">433</span>      }<a name="line.433"></a>
<span class="sourceLineNo">434</span>    }<a name="line.434"></a>
<span class="sourceLineNo">435</span>    int oldValue = existingCounter.get();<a name="line.435"></a>
<span class="sourceLineNo">436</span>    if (oldValue == expectedOldCount) {<a name="line.436"></a>
<span class="sourceLineNo">437</span>      if (oldValue == 0) {<a name="line.437"></a>
<span class="sourceLineNo">438</span>        if (newCount == 0) {<a name="line.438"></a>
<span class="sourceLineNo">439</span>          // Just observed a 0; try to remove the entry to clean up the map<a name="line.439"></a>
<span class="sourceLineNo">440</span>          countMap.remove(element, existingCounter);<a name="line.440"></a>
<span class="sourceLineNo">441</span>          return true;<a name="line.441"></a>
<span class="sourceLineNo">442</span>        } else {<a name="line.442"></a>
<span class="sourceLineNo">443</span>          AtomicInteger newCounter = new AtomicInteger(newCount);<a name="line.443"></a>
<span class="sourceLineNo">444</span>          return (countMap.putIfAbsent(element, newCounter) == null)<a name="line.444"></a>
<span class="sourceLineNo">445</span>              || countMap.replace(element, existingCounter, newCounter);<a name="line.445"></a>
<span class="sourceLineNo">446</span>        }<a name="line.446"></a>
<span class="sourceLineNo">447</span>      } else {<a name="line.447"></a>
<span class="sourceLineNo">448</span>        if (existingCounter.compareAndSet(oldValue, newCount)) {<a name="line.448"></a>
<span class="sourceLineNo">449</span>          if (newCount == 0) {<a name="line.449"></a>
<span class="sourceLineNo">450</span>            // Just CASed to 0; remove the entry to clean up the map. If the removal fails,<a name="line.450"></a>
<span class="sourceLineNo">451</span>            // another thread has already replaced it with a new counter, which is fine.<a name="line.451"></a>
<span class="sourceLineNo">452</span>            countMap.remove(element, existingCounter);<a name="line.452"></a>
<span class="sourceLineNo">453</span>          }<a name="line.453"></a>
<span class="sourceLineNo">454</span>          return true;<a name="line.454"></a>
<span class="sourceLineNo">455</span>        }<a name="line.455"></a>
<span class="sourceLineNo">456</span>      }<a name="line.456"></a>
<span class="sourceLineNo">457</span>    }<a name="line.457"></a>
<span class="sourceLineNo">458</span>    return false;<a name="line.458"></a>
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<span class="sourceLineNo">460</span><a name="line.460"></a>
<span class="sourceLineNo">461</span>  // Views<a name="line.461"></a>
<span class="sourceLineNo">462</span><a name="line.462"></a>
<span class="sourceLineNo">463</span>  @Override Set&lt;E&gt; createElementSet() {<a name="line.463"></a>
<span class="sourceLineNo">464</span>    final Set&lt;E&gt; delegate = countMap.keySet();<a name="line.464"></a>
<span class="sourceLineNo">465</span>    return new ForwardingSet&lt;E&gt;() {<a name="line.465"></a>
<span class="sourceLineNo">466</span>      @Override protected Set&lt;E&gt; delegate() {<a name="line.466"></a>
<span class="sourceLineNo">467</span>        return delegate;<a name="line.467"></a>
<span class="sourceLineNo">468</span>      }<a name="line.468"></a>
<span class="sourceLineNo">469</span><a name="line.469"></a>
<span class="sourceLineNo">470</span>      @Override<a name="line.470"></a>
<span class="sourceLineNo">471</span>      public boolean contains(@Nullable Object object) {<a name="line.471"></a>
<span class="sourceLineNo">472</span>        if (object == null) {<a name="line.472"></a>
<span class="sourceLineNo">473</span>          return false;<a name="line.473"></a>
<span class="sourceLineNo">474</span>        }<a name="line.474"></a>
<span class="sourceLineNo">475</span>        try {<a name="line.475"></a>
<span class="sourceLineNo">476</span>          return delegate.contains(object);<a name="line.476"></a>
<span class="sourceLineNo">477</span>        } catch (ClassCastException e) {<a name="line.477"></a>
<span class="sourceLineNo">478</span>          return false;<a name="line.478"></a>
<span class="sourceLineNo">479</span>        }<a name="line.479"></a>
<span class="sourceLineNo">480</span>      }<a name="line.480"></a>
<span class="sourceLineNo">481</span><a name="line.481"></a>
<span class="sourceLineNo">482</span>      @Override<a name="line.482"></a>
<span class="sourceLineNo">483</span>      public boolean containsAll(Collection&lt;?&gt; collection) {<a name="line.483"></a>
<span class="sourceLineNo">484</span>        return standardContainsAll(collection);<a name="line.484"></a>
<span class="sourceLineNo">485</span>      }<a name="line.485"></a>
<span class="sourceLineNo">486</span><a name="line.486"></a>
<span class="sourceLineNo">487</span>      @Override public boolean remove(Object object) {<a name="line.487"></a>
<span class="sourceLineNo">488</span>        if (object == null) {<a name="line.488"></a>
<span class="sourceLineNo">489</span>          return false;<a name="line.489"></a>
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<span class="sourceLineNo">491</span>        try {<a name="line.491"></a>
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